Spark plug terminal

ABSTRACT

A spark plug terminal having an initially tubular body portion between its ends is provided with an axially elongated indentation in one side thereof, the maximum depth of the groove being such that the inner surface of the indentation bears against the inner surface of the diametrically opposed side of the body portion and the width of the indentation being such that the sides of the latter engage the corresponding sides of the body portion. The body portion may remain axially straight or it may be bent between its ends to form an elbow, the direction of bending being such that the groove is at the inside of the elbow. One end of the terminal is provided with means for attaching it to a conductor and the opposite end of the terminal is provided with means for connecting it to the electrode of a spark plug. A sleeve or boot of dielectric material is assembled with the terminal.

[ 1 May 28, 1974 1 SPARK PLUG TERMINAL [75] Inventors: Howard A. Elliott, Detroit; Stephen J. Grebik, Roseville, both of Mich.

[73] Assignee: Essex International, Inc., Fort Wayne, 1nd.

221 Filed: Feb. 11, 1972 21 Appl. No.: 225,581

[52] US. Cl 339/259 R, 29/630 A, 72/369 [51] Int. Cl HOlr 11/22 58] Field of Search 339/256, 258, 259, 262,

339/252, 97 S, 136 C, 140 S, 143 S, 149 S, 213 S, 217 SP, 218 S, 220 A, 223 S, 255 B, 263 S, 278 T; 29/630 R, 630 A, 630 C, 630

[56] References Cited UNITED STATES PATENTS 2,285,275 6/1942 Harder 72/369 Great Britain 339/258 R Japan 72/369 Primary Examiner-Bobby R. Gay' Assistant ExaminerLawrence .l. Staab [57] ABSTRACT A spark plug terminal having an initially tubular body portion between its ends is provided with an axially elongated indentation in one side thereof, the maximum depth of the groove being such that the inner surface of the indentation bears against the inner sur face of the diametrically opposed side of the body portion and the width of the indentation being such that the sides of the latter engage the corresponding sides of the body portion. The body portion may remain axially straight or it may be bent between its ends to form an elbow, the direction of bending being such that the groove is at the inside of the elbow. One end of the terminal is provided with means for attaching it to a conductor and the opposite end of the terminal is provided with means for connecting it to the electrode of a spark plug. A sleeve or boot of dielectric material is assembled with the terminal.

15 Claims, 17 Drawing Figures SPARK PLUG TERMINAL The invention disclosed herein relates to spark plug terminals and to their method of manufacture, and more particularly to spark plug terminals having improved structural and electrical characteristics and which are more easily and inexpensively produced than spark plug terminals currently in use.

New automotive engine designs make it necessary that spark plug terminals be longer than those previously in use so as to assist in conducting heat away from the well in which a spark plug is located. Most of the spark plug terminals utilized on automotive vehicle engines require that the terminal be bent between its ends so as to facilitate connection of the ignition wires to the spark plug electrodes. Conventionally, the terminals have parts of their bodies cut away to facilitate the bending of the terminals. The cutting away of the terminals for this purpose weakens the terminals, and the adverse effect of such weakening is magnified in the longer terminals presently required.

The necessity heretofore of cutting away portions of terminals has resulted in disadvantages other than the weakening of the terminals. For example, the cutting away of portions of a terminal means that the remaining portions of the terminal must conduct all of the current, thereby resulting in high current density with consequent heat generation. Moreover, cutting of a terminal frequently leaves sharp points or burrs which are objectionable electrically. Such burrs also are objectionable structurally in those instances in which a dielectric boot is fitted over the terminal inasmuch as the burrs can damage the inner surface of the boot as the latter is drawn over the terminal, thereby making it possible for dielectric failures tooccur at lower than permissible values.

Most of the bent terminals currently in use are bent along small radii so as to form a rather abrupt bend, as a consequence of which the dielectric boot must have a correspondingly abrupt bend between its ends. An abrupt bend in a dielectric boot subjects the latter to considerable physical stress, and it is not uncommon for sharply bent boots to fail structurally after a short period in service. This objection has been overcome to some extent in the past by preshaping a boot so that it initially has an angular configuration, but the cost of angular boots as compared to the cost of straight or axial boots is excessive.

A spark plug terminal constructed in accordance with the invention overcomes the disadvantages referred to above by making it unnecessary to cut a terminal body to enable it to be bent, thereby avoiding the formation of sharp points or burrs and avoiding weakening of the terminal, both structurally and electrically. Such a terminal, when bent. is bent about a large radius, as compared to the radii of conventional terminals, thereby making it possible to assemble an axially straight di-electric sleeve with the terminal without subjecting the sleeve to undue physical stress.

An object of this invention is to provide a spark plug terminal which need not be cut to enable its being bent, thereby avoiding the formation of sharp points and avoiding the structural and electrical weakening of the terminal.

Another object of the invention is to provide a spark plug terminal which can be bent about a relatively large radius, as compared to the radii of conventional termirials, so as to enable axially straight dielectric boots or sleeves to be assembled on the tenninal without subjecting the boot to undue physical stress.

A further object of the invention is to provide a method of manufacturing a terminal of the'kind described.

Other objects and advantages of the invention will be pointed out specifically or will become apparent from the following description when it is considered in con junction with the appended claims, and the accompanying drawings, in which:

FIG. 1 is a top plan view of a spark plug terminal constructed in accordance with the invention and illustrating the terminal prior to its being bent;

FIG. 2 is a bottom plan view of the terminal shown in FIG. 1;

FIG. 3 is an end elevational view of the terminal shown in FIG. 1 as viewed from the right-hand end thereof;

FIG. 4 is a view partly in side elevation and partly in section of a terminal fitted into a forming die and illustrating the first stage of a three-stage terminal bending operation;

FIG. 5 is a vertical sectional view taken on the line 5-5 of FIG. 4;

FIG. 6 is a bottom plan view of a terminal illustrating its appearance following the initial bending operation;

FIG. 7 is a view similar to FIG. 4, but illustrating the second stage of the three-stage bending process;

FIG. 8 is a vertical sectional view taken on the line 8-8 of FIG. 7;

FIG. 9 is a bottom plan view ofa terminal illustrating its configuration following the completion of the second stage of the bending process;

FIG. 10 is a view similar to FIG. 7, but illustrating the third stage of the bending process to obtain a bent terminal forming an included angle of about 130;

FIG. 11 is a vertical sectional view taken on the line llll of FIG. 10;

FIG. 12 is a side elevational view of a terminal illustrating its configuration following the third stage of the bending process, one end of the terminal being crimped to a conductor;

FIG. 13 is a fragmentary, isometric view of the terminal shown in FIG. 12 and particularly illustrating the inside of the elbow formed by the bending process;

FIG. 14 is a view similar to FIG. 12, but illustrating a terminal bent to fomi an included angle of about 1 10 and enclosed within a dielectric boot;

FIG. 15 is a side elevational view of a terminal bent to form an included angle of about FIG. 16 is a side elevational view of a slightly modified terminal; and

FIG. 17 is a sectional view taken on the line 17-17 of FIG. 16.

A spark plug terminal constructed according to the invention is formed from a blank of electrically conductive metal having at one end a flange which may be rolled into a substantially U-shaped connector 1 for crimping onto the end of an insulated spark plug wire 2 (FIG. 12). At its opposite end the blank has a flange which may be rolled to form a spark plug electrode socket 3. The confronting ends of the flange meet to form a split seam 4 and may be provided with interlocking fingers (not shown) as is conventional and which underlie a generally C-shaped spring clip 5 having a projection 6 adjacent each end thereof which extends through correspondingly spaced openings 7 (FIG. 12) formed in the flange so as to enable the projections to provide yieldable gripping means for the electrode (not shown) of a spark plug.

Between the opposite ends of the blank is another flange which is rolled to form a generally cylindrical, tubular body portion 8. The confronting ends of the flange forming the body 8 meet to form a split seam 9.

The blank from which the terminal is formed is notched at opposite ends of the body 8 as at 10 and 11 to enable flexure of the connector 1 and the socket 3 without causing corresponding flexure of the body 8.

The terminal shown in FIGS. 1, 2 and 3 is axially straight, i.e., not bent between its ends, and it may be used in this condition if desired. It is preferred, however, that the terminal be bent between the ends of the body portion 8 so as to facilitate its bridging the distance between the conductor 2 and the spark plug electrode.

Apparatus for bending the terminal comprises a first stage die 12 having a base 13 provided with a semicircular, axially extending groove 14 therein, the depth of the groove corresponding to half the outside diameter of the body portion 8. The die 12 also includes an upper or cover member 15 having an axially extending, semicircular groove 16 in its lower surface which mates with the groove 14 and forms a cylindrical cavity for the reception of the body portion 8. The die cover 15 has an axially extending slot 17 which communicates with the groove 16 along the longitudinal center line of the latter, the length of the slot 17 corresponding substantially to the length of the body portion 8. To condition the die for use, the cover 15 is removed, a terminal is fitted into the groove 14 with the seam 9 lowermost, and the cover 15 is replaced.

Adapted for use with the die 12 is a first stage forming punch 18 which may be supported on the reciprocable platen (not shown) of a press or the like. The punch has a depending tongue 19 of such size as to fit freely within the slot 17 and of such height as to correspond substantially to the distance from the base 14 to the upper surface of the cover 15. The tongue has a lower surface 20 which is arcuate both longitudinally and transversely. The longitudinal radius of the surface 20 corresponds to one-half the width of the tongue, so as to form a smooth curve from one side to the other of the tongue, and the transverse radius of the surface 20 corresponds to one-half the thickness of the tongue so as to form a smooth curve from one face to the other of the tongue. The thickness of the tongue 19 is substantially less than the diameter of the body portion 8. For example, if the wall thickness of the body portion 8 is 0.020 inch, and if the inside diameter of the body portion is 0.250 inch, the thickness of the tongue 19 may be 0.070 inch, or approximately 0.28 times the inside diameter of the body portion.

Movement of the punch 18 into and out of the die 12 results in an axial indentation 21 being formed in that wall of the body portion 8 which is opposite the seam 9. The indentation 21 is arcuate from end to end and has a maximum depth such that the inner surface of the indentation tangentially engages the inner surface of the seamed side of the body portion, but the side walls of the indentation 21 are spaced from the sides of the nondeformed portion of the body 8 as is shown in FIG. 5.

From the first stage die 12 the indented terminal is transferred to a second stage die 22 having a base 23 provided with a longitudinally extending groove 24 in its upper surface. The base 23 of the die 22 is identical in all respects to the base 13 of the die 12. The die 22 includes a cover 25 having an axial groove 26 complementary to and overlying the groove 24. The cover 25 has an axially extending slot 27 in communication with the groove 26. The axial length of the slot 27 corresponds to the length of the slot 17, but the width of the slot 27 is considerably greater than the width of the slot 17 so as to enable it to accommodate a tongue 28 of a punch 29, the punch 29 corresponding to the punch 18 except for the width of the tongue.

The lower surface of the tongue 28 is arcuate longitudinally and transversely. The longitudinal arc corresponds to the longitudinal arc on which the surface 20 of the tongue 19 is formed and the transverse arc of the tongue 28 forms a smooth curve from one face to the other of the tongue. The width of the tongue 28 corresponds substantially to the inside diameter of the body portion 8, less two wall thicknesses thereof. Thus, if the inside diameter of the body 8 is 0.250 inch, and if the wall thickness of the body is 0.020 inch, then the thickness ofthe tongue 28 may be 0.210 inch. It is preferred, however, to form the tongue 28 to a width slightly less than that specified above so as to allow for some tolerance in the wall thickness of the body 8. Normally a tolerance of 0.002 inch will be sufficient and, if this tolerance is provided, the width of the tongue 28 will be 0.208 inch, rather than 0.210 inch.

Movement of the tongue 28 into and out of the die 22 causes the side walls of the indentation 21 in the body 8 to be expanded into engagement with the side walls of the nondeformed portion of the body, as is indicated in FIG. 8, so as to produce a wider indentation 30. The width of the indentation 30 corresponds substantially to the inside diameter of the body 8, less two wall thicknesses.

Following completion of the formation of the inden tation 30, the terminal is transferred to a third die 31 having a base 32 provided with a generally V-shaped groove 33 in its upper surface, the diameter of the groove corresponding substantially to the original diameter of the body 8. The terminal is placed in the groove 33 with the indentation 30 uppermost. The groove 33 has its lowest point at the center of the die member 32 and those portions of the groove on opposite sides of the lowest point diverge upwardly uniformly. In the embodiment shown in FIG. 10, the groove portion on each side of the lowest point is inclined upwardly at an angle of 25, the two groove portions thus forming an included angle of The die 31 also includes a cover 34 having an axially extending slot 35 therein overlying the groove 33 and of such length as to accommodate a punch tongue 36 having an arcuate lower surface 37. The thickness of the tongue corresponds to the width of the indentation 30, but its axial width is less than that of either of the tongues 19 or 28. The axial width of the tongue 36 should be such as to enable the arc of the surface 37 to be formed on a radius corresponding to that on which the body 8 is to be bent and without stressing the opposite ends of the indentation 30. The axial width of the tongue 36, therefore, will vary depending upon the degree of bending to be imparted to the terminal body 8.

The length of the tongue 36 is such as to enable it to move into the die 31 a distance sufficient to engage the base of the indentation 30 and deform or bend the body 8 to conform to the V-shaped configuration of the groove 33. Thus, the opposite ends of the body portion form an included angle of 130.

Movement of the tongue 36 into and out of the die 31 will result in the terminals being bent about the central portion of the body 8 to form an elbow 38, as is shown in FIG. 12, with the indentation 30 lying at the inside of the elbow, as is best shown in FIG. 13. The presence of the indentation 30 at the inside of the elbow enables the body portion 8 to be bent smoothly and ironed" against the base of the groove 33 without the crimping which usually accompanies the bending of a cylindrical member at the inside of the elbow and without undue elongation of the metal at the outside of the elbow. The terminal shown in FIG. 12 has its body portion 8 bent along a radius of 0.375 inch.

The included angle between the opposite ends of the body portion will depend upon the extent to which the body is bent. Thus, FIG. 14 discloses a terminal having an included angle of 1 between the opposite ends of the body and the terminal shown in FIG. 15 has an included angle of 90 between the opposite ends of the body, but in both instances the radius of the elbow corresponds to the radius on which the elbow 38 is formed. It will be understood that the bending of the terminals such as those disclosed in FIGS. 14 and 15 necessitates substitution for the die 31 of other dies in which the terminal accommodating grooves are configured to form the desired included angle.

The terminal disclosed in FIGS. 16 and 17 is the same as those previously described except that the indentation is formed in one side of the body portion 8 which is spaced only 90 from the seam 9, rather than in the side which is diametrically opposite the seam.

Any of the terminals herein disclosed may be sheathed in a boot or sleeve 39, formed of dielectric material such as silicone rubber, which initially is axially straight, but which has sufficient resiliency to be slid over the terminal and conform to the angular configuration thereof. Due to the relatively large radius of the elbow 38, as compared to the diameter of the body 8, a silicone rubber sleeve may conform to the configuration of the terminal without being subjected to significant pinching at the inside of the elbow or significant tension at the outside of the elbow.

Inasmuch as no material is removed from the body 8 in order to enable its being bent, the structural strength of the body is not weakened. Moreover, all of the metal of the body is capable of conducting current, thereby avoiding high current density at the body portion of the terminal. The absence of the necessity of removing material from the body to enable its being bent, coupled with the *ironing" imparted to the body via the cooperating die members during the bending process, prevents the formation of sharp edges or burrs which could shear the boot 39 during its assembly with the terminal.

This disclosure is representative of presently preferred terminal constructions and methods of their manufacture, but is intended to be illustrative rather than definitive thereof. The invention is defined in the claims.

We claim:

1. An electrical terminal comprising an uninterrupted tubular, electrically conductive body and connector means at opposite ends of said body for connection to electrical terminals, said connector means being notched adjacent the opposite ends of said body, said body being deformed radially inwardly thereof between its ends and from one side of said body toward the opposite side thereof to form an elongate, axially arcuate indentation of less width than the diametral dimension of said body, said indentation having a bottom and opposed sides, the bottom of said indentation at its deepest point being in face to face engagement with the opposite side of said body and the opposed sides of said indentation at said deepest point being in face to face engagement with the respective adjacent sides of said body, whereby the entire deformed wall portion of said indentation at the deepest point thereof is in face to face engagement with the entireundeformed wall portion of said body at said point.

2. A terminal according to claim 1 wherein said indentation is arcuate transversely of said body.

3. A terminal according to claim 1 wherein said body is bent between its ends to form an elbow, said indentation being at the inside of the elbow.

4. A terminal according to claim 3 wherein said body forms an included angle of substantially 5. A terminal according to claim 3 wherein said body forms an included angle of substantially 6. A terminal according to claim 3 wherein said body forms an included angle of substantially 7. A terminal according to claim 1 wherein said body is split longitudinally, said split and said indentation being located on opposite sides of said body.

8. A terminal according to claim 1 wherein said body is split longitudinally, said split and said indentation being spaced substantially 90 from one another.

9. A terminal according to claim 1 wherein said body is substantially cylindrical in cross-section except for said indentation.

10. A terminal according to claim 1 wherein said body forms an included angle greater than 130. and less than 11. A method of making an electrical terminal having between its ends a cylindrical, elongate body formed of electrically conductive material, aid method comprising deforming one side of said body between its ends radially inwardly of said body toward the opposite side thereof to form an elongate, axially arcuate indentation having a predetermined radius such that the deepest point of said indentation is in face to face engagement with the opposite side of said body, said indentation being of such width that at said deepest point thereof the opposed sides of said indentation are in face to face engagement with the respective ajdacent sides of said body; and bending said body at said deepest point of said indentation about a radius less than said predetermined radius to form an elbow between the ends of said body, the direction of bending said body being such that said indentation is at the inside of said elbow.

12. A method according to claim 11 wherein the bending of said body forms an included angle less than 180.

13. A method according to claim 11 wherein said body is bent about an are having its center at the center of the arc of said indentation.

14. A method according to claim 11 wherein the 15. A method according to claim 11 wherein the depth of said indentation corresponds to the inside dibending of said body forms an included angle of beameter of said body less the wall thickness of said body. tween about 90 and abkout k 132.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION May 28, 1974 Patent No. 6 5 Dated Inventor(s) Howard Elliott, t al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 11, line 3, change "aid" to said line 12, change "ajdacent" to adjacent Signed and sealed this 1st day of October 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 9 ORM O 69) USCOMM-DC 60376-P69 fi' UTS, GOVERNMENT PRINTING OFFICE I I9, 0-35533l. 

1. An electrical terminal comprising an uninterrupted tubular, electrically conductive body and connector means at opposite ends of said body for connection to electrical terminals, said connector means being notched adjacent the opposite ends of said body, said body being deformed radially inwardly thereof between its ends and from one side of said body toward the opposite side thereof to form an elongate, axially arcuate indentation of less width than the diametral dimension of said body, said indentation having a bottom and opposed sides, the bottom of said indentation at its deepest point being in face to face engagement with the opposite side of said body and the opposed sides of said indentation at said deepest point being in face to face engagement with the respective adjacent sides of said body, whereby the entire deformed wall portion of said indentation at the deepest point thereof is in face to face engagement with the entire undeformed wall portion of said body at said point.
 2. A terminal according to claim 1 wherein said indentation is arcuate transversely of said body.
 3. A terminal according to claim 1 wherein said body is bent between its ends to form an elbow, said indentation being at the insIde of the elbow.
 4. A terminal according to claim 3 wherein said body forms an included angle of substantially 90*.
 5. A terminal according to claim 3 wherein said body forms an included angle of substantially 110*.
 6. A terminal according to claim 3 wherein said body forms an included angle of substantially 130*.
 7. A terminal according to claim 1 wherein said body is split longitudinally, said split and said indentation being located on opposite sides of said body.
 8. A terminal according to claim 1 wherein said body is split longitudinally, said split and said indentation being spaced substantially 90* from one another.
 9. A terminal according to claim 1 wherein said body is substantially cylindrical in cross-section except for said indentation.
 10. A terminal according to claim 1 wherein said body forms an included angle greater than 130*. and less than 180*.
 11. A method of making an electrical terminal having between its ends a cylindrical, elongate body formed of electrically conductive material, aid method comprising deforming one side of said body between its ends radially inwardly of said body toward the opposite side thereof to form an elongate, axially arcuate indentation having a predetermined radius such that the deepest point of said indentation is in face to face engagement with the opposite side of said body, said indentation being of such width that at said deepest point thereof the opposed sides of said indentation are in face to face engagement with the respective ajdacent sides of said body; and bending said body at said deepest point of said indentation about a radius less than said predetermined radius to form an elbow between the ends of said body, the direction of bending said body being such that said indentation is at the inside of said elbow.
 12. A method according to claim 11 wherein the bending of said body forms an included angle less than 180*.
 13. A method according to claim 11 wherein said body is bent about an arc having its center at the center of the arc of said indentation.
 14. A method according to claim 11 wherein the depth of said indentation corresponds to the inside diameter of said body less the wall thickness of said body.
 15. A method according to claim 11 wherein the bending of said body forms an included angle of between about 90* and about 130*. 